Combination process for the cracking and destructive hydrogenation of hydrocarbons



Feb. 18, 1947.`

A. L. FOSTER COMBINATION PROCESS FOR THE CRACKING AND DESTRUOTIV'EHYDROGENATION OF HYDROCARBONS sheets-snelst 1 INVENTOR A L. FOSTER BY jATTOR Feb. 18, 1947.

A. L. FOSTER 2,415,998

COMBINATION PROCESS FOR THE CRACKING AND DESTRUCTIVE HYDROGENATION OFHYDROCARBONS Filed May`l7, 1945 3 Sheets-Sheet 2 AL. FOSTER ATTO Feb.18, 1947. A. FOSTER 2,415,998

COMBINATION PROCESS FOR THE CRACKING AND DESTRUCTIVE I HYDROGENATION 0FHYDROCARBONS Filed May 17, 1945 :s sheets-sheet :s

R TERMAl. CRACK-GAS REvERsmN/ |52 '53/|+\HEAv|Es FLASH CHAMBE INVENTOR Im A.| FOSTER Il BY EYS W JU ATTO Patented Feb. 18, 1947 COMBINATIONPROCESS FOR THE CRACK- ING AND DESTRUCTIV E HYDROGENATION OFHYDROCARBONS Arch L. Foster, Tulsa, Okla., assignor to PhillipsPetroleum Company, a corporation of Dela- Ware i Application May 17,1943, Serial No. 487,364

1 Claim. 1

This invention relates to the treatment of ipetroleum hydrocarbons forthe purpose of converting crude materials into finished products. Morespecifically it relates to the conversion of hydrocarbons by catalyticand non-catalytic means and to the intercorrelation of particulartreatments of definite fractions of crude petroleum to give improvedyields of high octane number motor fuel stock.

Modern refinery technology requires that crude petroleum, before beingprocessed further, shall be divided into various fractions suitable fordifferent purposes which may be processed in different ways to yieldsimilar or different products. Furthermore, during the processing ofthese different fractions, intermediate materials are formed which areordinarily considered by-products or waste materials, unprocessibleformaking the main product from the given reaction which, however, maybe processed further in a different manner to yield marketable products.In some cases such intermediate or by-products from two or moreprocesses may be combined in such manner as to yield another product.otherwise not made, converting a low-grade or waste material intovaluable products to improve the efficiency of the process.

A primary object of my invention is to produce high yields of valuablehydrocarbons suitab-le for use as motor fuel. Another object is toprovide increased yields of motor fuel from heavy components of crudeoil. Another` object is to combine and correlate certain processes andmaterials in such manner as to produce new materials therefrom, toutilize all waste products to the highest advantage, and to producelarge yields of the most valuable products. A further object is to treattogether gaseous and heavy residual products obtained by distillation ofcrude petroleum and from certain catalytic and noncatalytic hydrocarbonconversion processes in such manner as to give optimum yields of highoctane number motor fuel stock. Yet another object is to provide amethod for the production of motor fuel hydrocarbons from heavierhydrocarbons which are not ordinarily treated to give motor fuelhydrocarbons. Further objects and advantages of the invention will beapparent from the accompanying disclosure and discussion.

In a preferred .practice of my invention, a crude petroleum is separatedby fractionation into a number of fractions comprising at least (a)pentanes and lighter, (b) gasoline or naphtha, (c) gas oil, and (d)residuum. Fraction (a) is passed to a second fractionator in admixturewith satiii) vurated and unsaturated C5 and lighter hydrocarbons andusually some hydrogen from other conversion steps described below, andthe admixture therein separated into fractions including a C3 andlighter gas. The fourand iive-carbon-atom hydrocarbons are recoveredtogether or separately from said fractionator, a portion thereofcatalytically dehydrogenated followed by separation of hydrogen andolefins, and said hydrocarbons including said olefins subjected tocontrolled alkylation which will be described more fully hereinafter.The C3 and lighter gas mentioned above is heated and admiXed with theresiduum (d) and the mixture flashed, with separation of gas and liquidphases. The gas phase is maintained under reaction conditions such as toeffect a non-catalytic gas reversion type of conversion producing lightgases, motor fuel, and heavier hydrocarbons.

The liquid phase is admixed with hydrogen from the aforementionedcatalytic dehydrogenation and subjected to destructive hydrogenationwhereby it is converted in large part to motor fuel and hydrocarbonsamenable to catalytic cracking. Said hydrocarbons, in admixture withheavier hydrocarbons from said gas reversion and with virgin gas-oilseparated from the crude petroleum as fraction (c), are subjected tocatalytic cracking to give high yields of motor fuel. Light gasesproduced as by-products are passed to the aforementioned secondfractionator. Fraction or fractions (b) are subjected'to catalyticreforming to give higher octane number motor fuel, and any light gasespassed to said second fractionator. Additional features include thenon-catalytic cracking of cycle stocks separated from catalyticcracking.

The accompanying drawing, along with the description thereof, isprovided to aid in the understanding of the various aspects andintercorrelations of my invention, and exemplifies a preferredmodification thereof. It will, of course, be understood that theinvention is not limited to the exact arrangement shown, since variousother modifications are indicated herein or willv be obvious to oneskilled in the art in ,view of the disclosure herein. The drawing showsdiagrammatically an arrangement ofV apparatus, not necessarily drawn toscale, suitable for carrying out treatment of hydrocarbons in accordancewith my invention. The single drawing, for the sake of clarity,comprises three sheets, numbered Figures 1A, 1B, and 1C, with linesinterconnecting between the sheets as shown. v

Raw crude oil or other charge of Wide boiling range, heated to thedesired temperature in any convenient manner not shown in the drawing,enters through line I and is flashed in crude fractionator 2. By methodswell known to the art the charge is divided into a plurality ofoverhead, side, and bottom streams, such as the six shown in the figure:line ||2| carries pentanes and lighter hydrocarbons, line |02 carries alight gasoline fraction of up to 275-300 F. end point, line |03 carriesa heavy naphtha boiling up to 450 F. or higher, line |04 carries akerosene-light gas oil fraction with, for example, a E50-600 F. endpoint, line |05 carries a heavy gas oil fraction, and line |06 carries amedium or heavy residuum of any desired specifications. The crudeorothercharge may be sub-dividedinto 'any desired combination of fractions tomeet the requirements oi the operations without departing from theprinciples of the invention.

The C5 and lighter stream passes from fractionator 2 via line lill intoan ecient fractionator 3, 3

4 .to .further use as will be explained later. Any

portion not required for such usemay be withdrawn through line 'i0foruse .asfuel A portion of the C3 and lighter `strearn mayrlie-,continuously bled off, as by line 'Ill or line lut, to avoidpyramiding of hydrogen and/or methane in the system. VIt may sometimesbe desirable to` separate a .lightest fraction comprising Vhydrogen andwhich also may comprise methane, via `lines 9.9 and `||l|i,.a portion ofwhichmay ybe passedto line 4 if desired, with another .fractioncomprising C2 and C3, and also .methane if desired, Ybeing separated viaylines .98 and 4. The ,kettle product from fractionator 3 is passed vialine |98 to fractionatorli, wherein C4-s.are separated from Css Thebutane-butene fractionis carried overhead through .line 5 intofractionator 1 wherein isobutane `and at least part, and preferablysubstantially --all, of the isobutylene and butene-l, are separated asan overhead .product which is carried through line 8 to alkylation unit9. The normal butane together with .butenes-,Z and any other butenes.not taken voi overhead are withdrawn as kettle product from column 1via line I3 and passed to a catalytic dehydrogenation system indicateddiagrammatically at .i This` system comprises the usual furnaces,catalyst chambers, catalyst regeneration means, and other equipmentwellknown to the art, which need not be recited here in detail. fThedehydrogenation may be carried .out without Vtheaid of catalysts, butthis is generallyless desirable, inthat agreater variety of products andpoorer eiiiciency isob- .tained AThe hydrocarbons to 'be dehydrogenatedare preferably passed 'at theidesired temperature, generallyinthe rangeof.,'950.to `1150" and ow rate, suchas space velocities from 50t0 2000,over aneicient dehydrogenation catalyst, such as one of thechromia-alumina catalysts now widely used for this purpose, and the.dehydrogenation'products areintroduced ,via .line .|98 intofractionating systemr lill, from which V.hydrogen is separatedvialine|22 to be used in the destructive hydrogenation step of the process' as.described below. System .fl It `ordinarily Acomprises a singleormultiple-stage scrubbing, combined With'fraction- 4 ation in one or moreconventional columns. The butenes formed in the dehydrogenation, plusany butenes fed thereto, are passed from unit IU via line i3 toalkylator 9. These butenes may be separated in unit I@ from anyundehydrogenated normal butane which is recycled to the dehydrogenationunit Ordinarily, however, this is not done, the entire C4 hydrocarboncontent of the dehydrogenation eiliuents being passed to the alkylationstep, wherein the normal butane may take part in the alkylationreaction, although kmore often, and preferably, it acts merely as adesirable or at least innocuous diluent.

In alkylation unit 9, the isobutane is alkylated by the butenesin anymanner known to the art, to give a very high octane number substantiallysaturated motor fuel blending stock. Preferably 'a liquid catalyst suchas sulfuric acid, or especiallyhydrouoric acid, is used, at atmosphericor near-atmospheric temperatures, and with suicient pressure to maintainthe entire .reaction mixture in iiquidphase. .The ratio of isoparain toolelinis kept at a value well above 1:'1, and frequently as high as :1or even higher, depending upon the particular method of contactinghydrocarbons with acid and upon other characteristics of the alkylationsystem. Theart ci alkylation is now Vwell developed .and accordingly thevarious details for 4carrying'out the alkylation itself need not bediscussed further. Hydrocarbons effluent from .the .alkylation arepassed via line to fracti'onator I4, wherein a separation is madebetween the alkylate product, comprising C5 and heavier,whichleavesthrough line H2, and C4 hydrocarbons, :generally vconsistingentirely of isoand normal butane, which are recycled by means of line I3to one or more desired points in the fractionation and alkylation systemjust described. According to the composition of the stream in line ||3and of the other streams, a portion or all may be reintroducedthroughline H4 for introduction to alkylator 9, line H5 fordehydrogenation in unit Il, or line H for separation into isoand normalcomponents in fractionator 1, from which it again is passed Yalong withother hydrocarbons for dehydrogenation and/or alkylation as described.

It is to be understood that throughout the process disclosed hereinvarious auxiliary steps of intermediate or secondary -fractionations orseparations other vthan thosedescribed may be employed, such as settlingand Vrecycling of mobile catalyst, separation of catalyst fromhydrocarbons, 'separating reacted product from unreactcd material whichmay be recycled, separating by-products from `other desired products,and other ysimilar steps which may be required in practice to promoteyefficiency and increase yields of primary products. All of rsuch stepslare `not shown herein, their use being indicated by, or being Yobviousto one skilled in the art in View of, the disclosure herein,

A pentan'e-pentene fraction is obtained as bottom product fromfractionator 5 through vline 22,

" andis subjected'to the same Vtype ofptreatment as thatjust describedfor the butane-butene fraction obtained as top product from iraetionator5, but under conditions chosen as optimum jfor the particular C5hydrocarbons being treated, jwhich are generally different from theoptimum `conditions for the same operations on C4 hydrocarbons` MaterialHows from line 22 into fractionatorv23f, iso-C5s, particularlyisopentane, are `taken ofi overhead via line 24 ,and passed toalkylator2 5,

, higher boiling Css, particularly normalvpentane,

tenes, preferably through the aid of a suitable alkylation catalyst asdescribed above with reference to theC4 alkylation step, and eiuenthydrocarbons are then passed via line |22 to fractionator 29. Thealkylate, a high octane number saturatedxmotor fuel stock particularlysuited for -use in aviation fuels, is withdrawn via line 3|.

All or a part of the unreacted Cas, which are usually substantially freefrom olefins, may be lwithdrawn as part of the alkylate to give adesired volatility thereto, and/or may be separated overhead, as by line30, for recycle in a manner similar to the C4 recycle from line ||3 asheretofore explained. For this purpose lines |23, |24, and |25 areprovided, leading from line 30 to alkylator 25, dehydrogenator 21, andfractionator 23, respectively.

Frequently it is desirable to separate out a substantially pureisopentane fraction for use as a blending agent for aviation fuelsinasmuch as isopentane has a high octane number and at the same time ishighly volatile. Such a fraction may be separated' out via line 26. Whenthe pentene content of the feed to fractionator 23 issuficiently low, orsuch that pure, olefin-free isopentane can be separated therefrom, suchisopentane may be taken oil! overhead through line 24, with part beingdiverted to line 26 for the purpose stated. More often, however, sucholefin-free isopentane blending stock is best obtained from thealkylation effluents by fractionation in column 29, the alkylation thusserving to remove pentenes from admixture with the isopentane.

lIn this instance, isopentane may be taken as a top product through line3U, with part or all passing via line |21 to line 26, while normalpentane is separated from fractionation system 29 via. line |28 andrecycled via line 30 to one or more desired points either alone or inadmixture with some isopentane. The relative amounts of isopentane usedup in the alkylation step or separated as blending agent will of coursedepend upon the available supply thereof from the crude oil or othercharge stock and from the various conversions soon to be described, aswell upon the properties desired of the finished motor fuel blend orblends produced by my invention.

A modification of the alkylation steps just discussed which is sometimespreferred because of the relative amounts of the various hydrocarbonsavailable, other uses to which certain of the hydrocarbons may be put,or certain properties of `valkylate which it is desired to obtain,involves the alkylation of isobutane with pentenes and/or thismodification may be taken advantage of is when butenes are needed foranother use, such as a dehydrogenation feed for the production ofbutadiene to be used in producing a synthetic rubber or the like, andwhen isopentane is more valuable as an aviation fuel blending stock thanas alkylation feed. In this case, only alkylation unit 9 is operated, ona butane-pentene feed, while butenes and isopentane are sent to theirrespective utilizations instead of being subjected to alkylation.Furthermore, when one or the other of the two alkylation systems isoverloaded or underloaded due to a particular mannerpin which thevarious conversions-are being operated, a portion of fresh charge orrecycle charge or both, comprising parafns and/or oleiins, may bediverted through lines shown and/or by means not shown, from one systemto the alkylation unitl of the other system, and the two charges maythus be at least partially comingled with the production of a mixedalkylate. This type of operation may be utilized over a wide range ofconcentrations without departing from the limits of the invention asdescribed and claimed, and allows a very desirable flexibility incarrying out the over-all operations. When any of these varousmodifications are practiced it may be desirable to recycle streams ofunconverted hydrocarbons containing both 4- and 5-carbon atomhydrocarbons back to fractionator 5 for separation into the two familiesof C4 and C5 hydrocarbons prior to further treatment, and for thispurpose lines ||1 and |26 are provided.

While I have referred primarily to alkylation of isoparaillns, it shouldbe understood that IA may also alkylate normal paraiiins under somecircumstances, by either catalytic or non-catalytic means known to theart. Conditions necessary are usually more severe than with isoparaflinalkylation, and the choice will depend upon the relative availability ofthe various C4 and C5 hydrocarbons. Furthermore, While I have shownspecific steps for separation of paraflin's from' olefins and the like,other steps, includingv those such as selective solvent extraction andthe like as Well as conventional fractionation, may be utilized,depending again upon the relative proportions of the varioushydrocarbons, and on the particular fractions Vit may be desired toseparate out for a certain alkylation or other conversion orutilization. In some cases a portion of the C3 hydrocarbons comprisingpropylene may be passed to alkylation along with butenes and/orpentenes. The extent t'o which dehydrogenation will be used to provideolefin feed for the alkylations is indirectly at least a function of theconversions of heavier hydrocarbons effected in other portions of thesystem. Generally these conversions are such that, although highlyolefinic gases are formed, there is still an excess of paraiiinsavailable for alkylation feed stock, thus making possible the use ofcatalytic dehydrogenation of the same to increase the ultimate yield ofalkylate. Turning now to the hydrocarbons in the crude oil having morethan five carbon atoms to the molecule, it will be seen fromthe drawingthat each of the fractions |02, |03, |04, and-|05fis treated separatelyin a catalytic conversion step to produce optimum yields of desiredhydrocarbons, usually those boiling .-in the motor fuel range. Muchhigher ultimate yields of desired products are obtainablethroughcatalytictreatr ment of these fractionsthan` would be vobtain.,-

vable if .they vwere treated by non-catalytic eonvversion processesexclusively.

The .light gasoline fraction separated from'still 2 via .line `|02 isheated by lmeans not shownto a reforming temperature such as 900 to 1050F., and passed into unit |29 atailow rate preferably in the range of 10to 20 barrels of liquid charge peiahour per ton of catalyst over asuitable reforming catalyst such as bauxite, alumina `having Aa smallproportion of chromium oxide associated therewith, or others such'asthose well-known to vthe art, whereby an appreciable improvement inoctane number of the gasoline maybe obtained while sufferingcomparativelysmall loss inl -yield of `|gasoline. Reforming v.eiliu-ents-are passed `via line |--to-stabilizer |3'| wherein light gases,primarily hydrogen, are separated overhead Via line .|32 for passage toline Ill-|- and thence to fractionator `3, while-'the'reformed gasoline'product is takenvialine- |33 for vblending with other gasoline productsproduced elsewhere vin the system. Ordinarily no appreciable amount ofmaterial heavier 4than gasoline is formedand thus no prolvisions need bemade for separating out such material. D

The heavy naphtha fraction obtained through line L|03 is ,subjected inknown manner to catalytict-rea-tment in unit 35, conditions preferablybeing'suchl l.that `an effect 'somewhat intermediate simplenon-destructive reforming and-.cracking is obtained. The catalyst may beprimarily a reforming ycatalyst similar to that used in unit |29, or itmay bezprimar-ily a cracking catalyst vsirnilarto -that `used in units4l and/or 55 to be described, vor it! may be a mixture of suchcatal-ysts or any other catalyst composition producing the desiredresults, the choice being Within the skillof the art in view oftheinstant disclosure. The reaction maybe such as to yproduce a desirablequantity of aromatic hydrocarbons.`

Reaction effluents vpass from unit 35 via line 36 into separator Y3i,ordinarily a single fractionator, wherefrommaterial boiling below adesired motor fuel yend point, such as 325 to425 F., is takencverheadvia lline 30 to fractionator 39,

vwhile heavier material is passed via line 42 to unit 6| fornon-catalytic ypyrolytic treatment, since this material is more amenableto such non-catalytic treatment than it is to a recycling operation tothe catalyst over whichl ithas already been passed. A reformed or'cracked gasoline is separated from column 39 via line 4|, whilelightgases, comprising/C4 or C5 and lighter hydrocarbons, .generally alongwith some hydrogen, are passed Vvia line to line |01 and 'fractionator3. v

The light virgin gas oil separated Afrom other constituents of the crudeoil is passed by way of line VHM into catalyticcrackingfunit 4l, whereinit is contacted with a suitable cracking catalyst at an elevatedtemper-ature generally in the range of '750 .to 11.00 F., at a lowsuperatmospherc pressure ranging" up to or 100 pounds per square inchgage, `and at a flow rate andother reaction conditions usually chosenfor optimum production of motor fuel hydrocarbons. The catalyst -ispreferably one of the so-called silicaalumina type, either synthetic ornatural, characterized by the presence of silica alongwith usu ally'relatively minor amounts of alumina, zirconia, and/or other metaloxides, and typified by silica'g'el activated'with adsorbed alumina onthe one hand and acid-washedv bentonite clay,v lsuch as Super-Filtrol,on the other. 'If-the productionof more `isoparaiiinsa'nd less olen's'is de'- sired, a .metal halide cracking'catalyst .such 'as aluminumchloride :may be used in'this and/or other cracking units.

It may be mentioned here that the catalytic re- 5 forming and/ orcracking units |29, 35, 4l, and 55, are merely illustrateddiagrammatically inthe drawing, and that in general any of these Yunits.may be of the fixed catalyst bed type, of .thefmoving catalyst bedtype,fas typified lby the so-called TCC process, or of the powderedcatalyst ,type typified by the so-ca1led fluid catalyst systems, orof'any other designwhich the leconomics of a particular situationindicate to be lmost desirable. While' the results obtained from .thesevarious typesof systems on a given charging stock :may vary to a limitedextent, it --may be said vthat .a given general result-may be obtainedfrom anyvof these systems, yandthe preciseoperating details Afor anysuch-catalytic system'will be readily supplied by one skilled in theart, vbased on the diS- jclosures herein of the materials treated andtheresults desired. It -is to be further understood that all of thenecessary equipment'for effecting catalyst reactivation, as by burningwith air 0r other oxygen-containing gas, is included inthe diagrammaticrepresentation, ysince `such equipment and the operation thereof are nowwell understood, and accordingly do not of themselves form part of thepresent invention. To show such Aequipment further would merely.complicatethe drawing without contributing appreciably to, theteachings of this disclosure. I l l Returning to the catalytic crackingsystem 41, reaction products, including unconverted gas oil, pass vialine |34 to fractionator'48, from the kettle of which is drawn cycle oilwhich is passedin whole or in part via line 5| into line 42 fortreatment in unit 6|. Cracked products are `taken overhead through line|35 into fractionator 449 from which a ycracked gasoline product of highantiknock value is `removed through line 50 while light gases,comprising predominantly oleins and isoparainns of five and/or fourcarbon' atoms and lighter oleiins, and usually very minor quan- I titiesof hydrogen and/or methane, are sent via lines |36 and |0'| tofractionator `3 -for separation yinto components and-utilization asspecied--else where herein. l y t Heavy virgin gas oil is vpassed via-line |05, vin 50 admixture lwith material from .lines-6B, 19,-and

S3 lprepared as hereinafter described, into catalytic unit-55, whereincracking is effected to produce motor fuel stock of good ant-iknockvalue. The catalyst in this 'case is again preferably -of the-silica-alumina'type, and will generally be derived from anatural clayrather than4 being syn,- theticall-y produced, since the life :of thecatalyst in this step fis 'frequently not so long as in the othercracking units shown, and thecost of synthetic catalyst is likely toexceed its 'value 'in obtaining any increased -eiliciency Reaction conditions` are similar 'to those used in unitJH. `Ordinarily, withcatalyst -of equal activity, 'a-lower temperature maywv be utilized incracking -the heavier hydrocarbons. Howeverfwith afless active catalystthe temperature in unit-55fmay beas high as, or even higher than, `thatin"unit 41. Cracked and unconverted hydrocarbons pass via line |31' intofractionation system 5B wherein residue higher boiling `than gasoline isseparated as kettle bottoms and passed lvia'lin'edi rto 'line-T42 Whereit is intermin'gled with other charge :stock passing tonon-catalytic'unit- 6|, while gasoline and lighter fractions are taken'overhead fromi56 via une ras wfracuonatoriei;familienaam fractionator,the desired high octane number motor fuel stock is obtained as kettleproduct, which is withdrawn through line 50, and light gases somewhatsimilar in composition to those obtained from fractionator 49 are takenthrough line 58 to line |01 for admixture and subsequent separation andtreatment with other light gases.

It will be seen from the above discussion that various cuts areseparated from the crude petroleum charged to the system, and those cutsranging from light gasoline to heavy gas oil are separately treated overcatalysts to give the desired yields of high octane number motor fuel.This separate treatment makes possible the choice of operatingconditions and catalysts optimum for each particular cut. In crackingunit 55 last described, not only is heavy virgin gas oil treated, .butalso in admixture therewith products obtained from three other stages inthe process, awhich are now to be discussed in detail.

After each of the catalytic treatments referred l to, a separation ismade, whereby light gases are separated and sent to a commonfractionator 3 in admixture with light material obtained from the crude,motor fuel is taken out, and heavy cycle stock is obtained. These cyclestocks are all shown as passing into line 42 for subsequent treatment inthermal cracking unit 6|. It is to be understood that I mayalternatively use a single, common fractionator for separating each ofthe streams |30, 36, |34, and |31 into the desired light gas, gasoline,and heavier cuts, rather than using the separate fractionators shown inthe drawing, and when the catalytic units are each operated on a highconversion per pass, or once-'through type of operation, I prefer topass the eiiiuents therefrom to a common fractionation system. However,it is sometimes more efficient tocatalytically reform and crack at arelatively low percentage conversion per pass, with recycle of Iat least`a portion of the unconverted material to vther catalyst for additionaltreatment to obtain a desired overall yield. For this purpose lines |39,|40, I4|, and |42 are provided. When this type offprocedure is used, itis preferable to use the` separate fractionators with each catalyticunitas shown, so that the proper cycle stock for each treatment will bemore readily obtained.

VIn all cases, however, I pass at least a portion of the cycle stock, orpartly converted or unconverted materials, to unit 6| for further,non-catalytic cracking. Recycle stocks from catalytic crackingoperations are rich in relatively saturated types of hydrocarbons, whichare more amenable to purely pyrolytic cracking than to further catalytictreatment, and thus the pyrolyticlcracking'of the cycle stocks referredto provides a more efficient operation and higher ultimate yield poffinal product than otherwise obtainable. Such cracking is eiected bypassing hydrocarbons from line 42 into thermal cracking unit 6|, whichis constructed and operated in a manner now well known to the art.Generally thev hydrocarbons are cracked under pressures of above 200pounds per square inch, ranging on up to 2000 pounds, and attemperatures of the order of 900 to l000 F. on up to as high as 1200 F.as may be desired. Light gases from line 4 may be introduced by meansnot shown into thecracking coils or reaction zone or elsewhere inthecracking unit 6| as desired to promote vaporization of the heatedcharge, to superheat the charge, and/or to promote gas reversionreactions.

Etlluents from 6| are passed via line |43 to fractionator 62, from whichgasoline and lighter products are passed overhead via line |44 to column'63, while cycle stock is separated via line |45. This cycle stock mayin part be returned via line |46 to unit 6| for further cracking inconventional manner, particularly When a relatively low per passconversion is being obtained therein. However, since the cycle stock isrelatively unsaturated and thus more susceptible to catalytio'than tofurther thermal cracking, a portion or all is passed via line 66 tocatalytic unit 55, and/or units 35 or 41, to be cracked therein withheavy virgin gas oil and other hydrocarbons as previously described. Ifthis recycle of thermaily cracked stock to catalytic cracking, and ofcatalytically cracked stock to thermal cracking were to be continuedindefinitely, the cycle stocks would become more and more refractory dueto the build-up of aromatics and other hydrocarbons which are notreadily cracked. Accordingly, a, portion of stream |45 is withdrawn fromthe system through lines |41 and |48. Heavy residues from thenon-catalytic cracking are also withdrawn from fractionation system 62through line |48. From fractiohator 63 light gases, highly oleiinic incharacter, are taken off overhead through line 65 for passage via line|01 to fractionator 3 in admixture with other light gases, while crackedgasoline product is separated through line 64. This product may beutilized as such, blended with other stocks, or subiected to catalyticaromatizing or other treatment designed to impart particular propertiesthereto.

Turning now to the residuum from crude iractionator Z, this materialpasses through line |06 to heater 1| and is heated to such temperatureas may be desired, up to that causing some cracking. Light gasesseparated via line il trom fractionator 3 as heretofore described, andincluding both paraflinic and oleiinic gases having three and lesscarbon atoms per molecule, and which also may include some hydrogen,although this is generally not preferred, are introduced via line 12into a separate coil in heater 1| and/or via line |49 into the liquidcharge line |06 prior to entry into a common heating coil. If heated ina separate coil the gases may be brought up to any desired temperaturehigher or lower than that employed for the liquid reduced crude charge,a'temperature as high as l200 F. being employed in some cases where themaximum vaporization of charge is desired. Both streams, or the streamscommingled through use of lines |49 or |50, are ashed in a vaporizingchamber 13, and all vapors pass therefrom via line |51 to thenon-catalytic cracking and gas reversion reaction zone 14. The gasesserve to superheat the liquid charge before or during hashing, to act assweeping agent in the vaporization thus giving maximum vaporization ofvolatile components of the residuum, and to take pai-t in the combinedcracking-gas reversion reaction in unit 14. Charge to this unit may beintroduced at any desired pressure and temperature, but preferablybetween about 500 'and 1500 pounds per square inch gage and about 850 to1000 F. A complex series of reactions takes place which may be regardedas a combination of cracking of heavy constituents and of lightsaturated constituents, along with polymerization of light olens.

Hot products from unit 14 pass via line |52 to fractionator 16, andvapors boiling in the gasoline range and kbelow pass overhead therefromthrough line 11 to stabilizer 18. The stabilized gasoline passes toblending or storage enlaces or for further treatment throughlline tp,While licht overhead ceses ness tiiroiieh line .il .to ir'inle withsimilar gases Yfrom otbleryunitis inline l''l' ior'passageto'fractionator 3. The gasoline trius'produced is"hi'ghly"olenic andpossessed 'of a' high antiknocl value. In vcase it is desired to producemaximum yields of aviation gasoline stocks; this particular gasoline is'especially s'uitedfor'use as fedstok'te'a catalytic treatment" whichwilleffectrng closure and other armatiziiig reactions; whereby' anaromatic 'st/o'ckveryuseful for 'increasing the antiknock value andricn'niixture performance of aviation fuels is obtained, V Recycle oiland insullciently cracked material, being olefl'nc'to a marked exetent,are"taken" from' fractionator is "tnrough line' 19 tocatalytio'crackin'g fumi 5,5 Where they are 'subjected' tofcatalyticcracking in ardmiggtu're With'heavyvirgin gas oil, ,cycle oil fromnonc'e'iolytifi "crociiiis 'finit '61, ,ond .the materiel de rkidaboVe;"'Havy refractory material siii eliicieckiiieiiinnit .5iWit'iidiolwn es bfc cinsircin fie iciiotcr li tiircofeli. .line .|53'.scoideci cii'eliffo portion tnereoi'moy so'iiie-tiines.'15enedvoiitoseoosly .recycled i9 line .|05 iiiesi 1111115 i310' 'iick'kili.not .snoivo- Tlienejev'i'f res liolnotctil frein 'the loottom oflfla'sli eliamb -4r .it is teken throne@ .1.' .e 1.5. to iii foei-notion.iiiiitti Wiieiein it 'isy `cciifriiiiirielec viitifiyiiioe'e ircinline1.2..,"obte1necl herein.- l 're""sli'c1fiecl, 'in ccniect with eiiicienthy,

genetica toVV produce nycirocar: .1.11 eeerectei and oi lower b, line sDess through line. .Si iectieeeted. in tower. sz

. u f. ne renee ,en

is produced e eosoline. prod. et

. Tee ses. accumulator 1. eieiioiniientlr of hydrogen, may fessee enti'ietiiroccl tofdestroctive hyf dioeeno'tioi iififiii.L iitiiroiieh. lineIii, while the 1101111 liieisefis taisen'vio llines 1.5i! end lil] toffii 3 i?? solicitation ond.. subsequent utillzatlon" Wiiiil'eiiie,invention hes ,been describes. in. some, detil'wiih reference to. inespecific exempte,

111i ietclbi' the drewine. 'it will be eooreiet'ed ny 'fanticos may loepracticed within lient ufheavy virgin 'on in unes igiene lpg respectVvely'may be treated together in a single catalytic crackingunit'; thesamefis Ytrue, of the' light gasoline and heavyV naiohtha'-n lines' H32and jlI-l respectively, and of'thehea'vy naphtha and lient ygals oiliinlines' Vl 03 and: Hill respectively,V

et?. FurthelIP-Qftlie cycle oils or` otherjprolineY ucts passingtlirjovugli lines iiigf'li and" Snmfafy i-.trlfiil materiel bonniesoci/e me" ih aline 155,. and' alieni ses .fraction Se@ endlessosVioline v1.5i to,

is" of litio.iiliiiftion-A iler exemple. tine` 12 orsi :be .seperated.into light Vand neatly fractions, h .are subsequently ,treated.separately as `in 4;? endior ne )lightand neat/yzrespee-Y tit/ely.-Wliile maximum Iyields of 1motor fuel hudrooarbons .are .generally.sought .and :obtained through `use `of frny invention, it gwill flee.seen that other products may Joe .obtained in increased yields .at the.expense .of motor iiuel .production Wheneeononiio .conditions .so.demand The nari.- ous .gasoline and .other products .will 'frequentlybe .blended together to `sive a final .composite motor fuel lout inineny Ynoses one 4or more .of tbe products .may be. utilized separately.Alsor many .oi the V,orooliicts and intermediate streams will reoeiyeadol' nal treatment, such .as .clay treating, vde.suliuiization, etc.,not .described .or shown, ,since .lille application of Ysuch treatmentis Wel-l understood in Atne art. .Qbyiously .many auxiliary .and .minorlsteps have been .omitted from this description, .since they .arewellYknown in the .and simply. ,constitute .good practice known .to .any...dl/laled y:.o'lesigner. yor operator. Various ,pieces lof equipment,including. .refluxv condensors .and .accumulators, reboilers, valves,pumps, compressors, heating and cooling means, heat exchangers, and thelike vhave not been shown in the drawingfor the sake of simplicity, Afew Valves lioie'eeeii indicated where ob.- viously alternative flows"might be used, but it will'lbe understood that no' attempt has ,beenmade to v'snow all pressure reducing Vorv other Valves. V

claim:

A process for the production of motor fuel stool; from heavyconwonentsfci crude Petroleum whichy combrisessenoroiins frein seidcrude Petroleum ay virgin 'gasoil anda 'residuum consisting o fl'iydrocarbonjs higher boiling than said gas oil, cash: me'soicl'resicliiiini in edinixtore with e lient. eescomprisingnydrocarbons of more than oneccarfbon'atom 'per moleculefat anelevated. teni'peatliij thereby e eos boese' ispioduced comprising saidlight `gas and volatile constituents of said i'csidiiim and el liquidphase is' riconosci-coole prising heavier constituents of said'residuum,seid lient ses comprising pereiiinic end; oleiinie gases produced inrst, second, and third conver-` sion stepshereinafter described,separating'said eesoiies'e 'and maintaining the .ccnipcneotlsfihere ciiii'iiist conversion step4 onder elevated tem:

peratu're 'endnressiirc usind for e suilicient timev in' o'neil-celelytic reaction, Zone to. effect. sub?. stantial production ofmotor fue] hydrocarbons, separating said motor fuelY hydro carbonsI as,"a precinct ci# the 'Processi .senoreltiins'A e 'irectioncihcaviiiydfocorbens so produced endsnbstenf tiallj free fromconstituentsboiling inl tlie range ofsaid residuurnand passingthe san-ie inadmiX-tu're With seid 'Virei 'feels 01.1 end al hjydr 11-.. solicitedmateriel 'of siiniiortoiline renee duced as leere.'inafter describedin', arse'cond con,-v veision 'step' iii Contact with ecieenegieeelystat cracking co'nditio'nsl to effect v'substanti@ pro. duction o'fmotorfuel' hydrocarbons, separating saidj'rioto'r` fuelhydrocarbons as`a'prcductof the""`niocess, subjecting seid.. liouiclnliese foro--` ducedby said flashing of said residuum and light gasto destructivehydrogepationin efthird con version step inadmijrture with`'hydr@gianYthe presence of Ia h'ydrogenatifon catalyst at elevated temperaturesandi pressures to produce "stubstan tial quantities oihydroc'arbonslower boiling'tlxan said. residuum, separating motorl fuel hydocarfbonsso produced as a product of the processi, andl f subjeQlf/.iiig tocracking as hereinbefore specified 13 14 hydrogenated hydrocarbons soproduced higher Number Name Date boiling than said motor fuelhydrocarbons but 2,129,506 Sachs Sept. 6, 1938 lower boiling than saidresiduum. 2,205,434 Phinney June 25, 1940 ARCH L. FOSTER. 2,319,354Sperling May 18, 1943 5 2,352,025 Seguy June 20, 1944 REFERENCES CITED2,256,615 Hederhorst sept. 23, 1941 The following references are ofrecord in the OTHER REFERENCES me of this patent' i Article entitledTechnique for Rening War UNITED STATES PATENTS 10 Products Explained, inThe Oil and Gas Jour- Number Name Date nal, of March 19, 1942, pgs. 19and 18. (Copy in 2,222,060 Arveson Nov. 19, 1940 196-49 of Division 3L)2,257,723 Arveson 0011 7J 1941 Flow Sheet inserted between pgs. 140 and141 2,300,691 @con N0v 3, 1942 of The Rener, of October 1942, v01. 21,No. 10. 2,303,107 Benedict Nov. 3, 1942 15 C0py in Div. 310 2,312,445Ruthruff Man 2, 1943 Williams, The Oil and Gas Journal, of Nov.

2,276,171 Ewell Mar. 10, 1942 7, 1935, DgS. 38 and 39. (Copy inScientific Lib.)

